Movement of the Small Intestine

The movement of the small intestine as elsewhere in the GIT can be divided into mixing contractions and propulsive contractions.

Mixing contractions(segment contractionns)

These are the most common type of intestinal contractions. When a portion of the small intestine becomes distended with chime, the stretching of the intestinal wall elicits localized concentric contractions. 

These segmental contractions are spaced at intervals along the intestine. The longitudinal length of each of these constructions is about 1-2cm.

During each segmentation about 1-2cm of the intestinal wall contracts forcing the chyme towards the colon, the segmentary movements also enable the chyme to mix with digestive juices and make contact with the absorptive surfaces of the intestinal mucosa.

Propulsive movements

Peristaltic waves help in the passage of chyme through the small intestine. These waves may occur in any part of the small intestine they move at a velocity of 0.5-1cm/sec and are faster in the proximal portion of the intestine and slower in the terminal portion of the intestine. They are very weak and usually die out after traveling 3-6cm. Normally it takes 3-5 hours for the passage of chyme from the pylorus to the ileocecal valve.

Peristaltic rush

In the peristaltic rush, very powerful and rapid peristalsis occur which travel along with distances in the small intestine within minutes. It rapidly sweeps the intestinal contents into the colon.

Causes

A peristaltic rush may occur due to severe irritation of the intestinal mucosa as infections diarrhea.